Object Disappears while Drag/Drop_C#

Hi,
I was trying drag drop from some tutorial.
Everything is working fine but just one thing is not.
While Dragging & Dropping from one place to the other object disappears.
When drops it appears on the perfect place where I have dropped it.
Let me tell you that the object is a prefab.
And there are slots where one can drag & drop objects from one place to the another.
Please help.
I am new to Unity & C#